Hydrocarbon conversion process for the production of olefins and aromatics

ABSTRACT

DISCLOSED IS A PETROLEUM REFINING PROCESS WHICH MAXMIZES PRODUCTION OF AROMATICS AND OLEFINS. PROCESS INCORPORATE HYDROCRACKING, CATALYTIC CRACKING, REFORMING. POLYMERIZATION, DEHYDROGENATION AND EXTRACTION OPERATIONS WITH MAXIMIZED CYCLING OF REFINERY STREAMS TO THE REFORMING AND DEHYDROGENATION PHASES.

United States Patent Int. Cl. C10g 13/02 U.S. Cl. 208-80 10 ClaimsABSTRACT OF THE DISCLOSURE Disclosed is a petroleum refining processwhich maximizes production of aromatics and olefins. Processincorporates hydrocracking, catalytic cracking, reforming,polymerization, dehydrogenation and extraction operations with maximizedcycling of refinery streams to the reforming and dehydrogenation phases.

RELATED APPLICATIONS This application is a continuation of our copendingapplication Ser. No. 28,271, filed Apr. 21, 1970, now abandoned, whichin turn was a continuation of our application Ser. No. 665,748, filedSept. 6, 1967, now abandoned, but copending at the date of filing ourSer. No. 28,271 application.

FIELD OF THE INVENTION The present invention relates to the conversionof hydrocarbons, such as petroleum oils, shale oils, tar sand oils, andcoal liquids to aromatics and olefins. More specifically, the presentinvention relates to an integrated petrochemical complex including unitsfor the production of aromatics and olefins and their separation as purehydrocarbons.

Still more specifically the present invention relates to a method forthe conversion of petroleum oils, shale oils, tar sand oils and coalliquids to aromatics and olefins, comprising; separating a crude mixtureto produce a C to C fraction, a C to 360 F. naphtha fraction, a 360 to600 F. light gas oil fraction, and a 600 F.+ residuum fraction;hydrocracking the residuum to produce a C and C fraction, a C to Cfraction, a C 360 F. fraction and a 360 F.+ fraction; catalyticallycracking the 360 F.+ fraction of the hydrocracker and the virgin 360 to600 F. fraction to produce a C and C fraction, a C to C fraction, a C to360 P. fraction, and a 360 F.+ cycle oil fraction; recycling the cycleoil fraction to the hydrocracking unit; combining the virgin C to 360 P.fraction with the C to 360 F. hydrocracking fraction and the C to 360 F.catalytic cracking fraction and subjecting the combination to catalyticreforming to produce a C and C fraction, a C to C fraction and a highlyaromatic reform'ate; solvent extracting the reformate to selectivelyremove aromatics and produce a non-aromatic rafiinate fraction, benzene,toluene, xylene and a C aromatic fraction; hydrodealkylating the tolueneto produce additional benzene; clay treating the benzene from reformingand hydrodealkylation; isomerizing the xylene and crystallizing theisornerizate to produce ethylbenzene and/or paraxylene by removingethylbenzene by fractionation, removing paraxylene from dimethylbenzeneby crystallization and recycling the dimethylbenzene to theisomerization unit, or recycling the ethylbenzene and dimethylbenzene tothe isomerization unit to extinction; separating pseudocumene from the 0aromatic fraction, removing dureue from the remaining material bycrystallization and isomerizing the residual product to 3,725,789Patented Apr. 10, 1S73 produce additional quantities or durene;polymerizing the C to C catalytic cracking product and the C to Cfraction of the reforming step to produce olefin polymers; hydrogenatingthe olefin polymers to produce isoparaffinio jet fuels and white oils;dehydrogenating C to C parafiins fromthe crude oils, the hydrocrackingstep, the reforming step and the polymerization-hydrogenation steps toproduce a parafiin-olefin mixture; recycling the parafifins to thedehydrogenation unit; and subjecting the olefins topolymerization-hydrogenation to produce additional jet fuel and whiteoil.

SUMMARY OF THE PRIOR ART In conventional petroleum refinery operations,the crude oil is passed to a distillation unit normally called a crudecolumn and the oil is fractionated into various cuts, including lightand heavy naphtha, light and heavy gas oil fractions, and a residuumportion boiling too high to vaporize in the crude column. This residualportion can be subjected to vacuum distillation or coking operations toproduce additional gas oil fractions.

Such conventional petroleum refining operations are generally conductedfor the purpose of maximizing the production of automotive gasoline.Therefore, the light and heavy naphthas are processed in a catalyticreforming unit to yield gasoline. The light and heavy gas oil fractionsare processed in a fluid catalytic cracking unit to yield gasoline andsome light olefin materials. The light olefinic materials and parafiinsare processed in a polymerization or alkylation unit to likewise produceautomo tive gasoline.

More recently, hydrocracking has been utilized to convert gas oils andcycle oils to automotive gasolines and middle distillates. As aconsequence of the utilization of hydrocracking, as indicated, reducedvolumes of olefins are being produced.

Finally, the separation of olefins and aromatics from the integratedrefinery streams is performed with the thought in mind that gasolineproduction will not be upset. Specifically, aromatic removal isselectively carried out so as not to reduce the octane value of thegasoline and olefin removal is selectively carried out so as not tointerrupt or upset the production of alkylation product which, likewise,is incorporated in automotive gasoline.

SUMMARY OF THE INVENTION In view of the foregoing, it is an object ofthe present invention to provide an integrated petrochemical complexwherein the full range of crude hydrocarbon oils are efiiciently andeffectively converted to petrochemicals. It is a further object of thepresent invention to provide an integrated petrochemical complex whereinthe full range of hydrocarbon crude oils is effectively and eflicientlyconverted to aromatics and olefins. It is a still further object of thepresent invention to provide an integrated petrochemical complex whereinaromatics are produced through high severity reforming and olefins areproduced through fluid catalytic cracking and dehydrogenation. Anotherand further object of the present invention is to provide an integratedpetrochemical complex wherein aromatics are further processed to yieldbenzene and paraxylene and reduced amounts of ethylbenzene, pseudocumeneand durene. Yet another object of the present invention is to provide anintegrated petrochemical complex wherein olefins are converted toisoparaffinic materials by polymerization and hydrogenation. Yet anotherobject of the present invention is to provide an integratedpetrochemical complex wherein light paraffins are converted toadditional volumes of olefins by dehydrogenation. Another object of thepresent invention is to provide an integrated petrochemical complexwherein light paraffins are converted to additional volumes of olefinsby dehydrogenation and the additional olefins are then converted topolyolefins by polymerization.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The single figure of thedrawings shows the integrated system of the present invention in blockdiagram form.

In accordance with the drawings, a crude oil such as petroleum oils,shale oils, oils derived from tar sands, oils derived from coal, as bysolvent extraction or carbonization, and like broad boiling range crudeoils are charged to a still 10 through line 12. In still 10, the crudeoil is fractionally distilled to separate C and C gases which aredischarged through line 14, a C fraction discharged through line 16, a Cto 360 F. (C fraction discharged through line 18, a light gas oilfraction boiling between about 360 and 600 F. discharged through line20, and a residuum boiling above about 600 F. discharged through line22.

The heavy residual fraction boiling above about 600 F. passing throughline 22 is discharged to a hydrocracking line unit 24. C and C gasesfrom the hydrocracking unit 24 are discharged through line 26, C to Cgases are discharged through line 28, a naphtha fraction from C to 360F. is discharged through line 30 and a light gas oil fraction boilingabove about 360 F. is discharged through line 32. The light gas oilfraction from the distillation unit 10 (in line and the gas oil fractionfrom the hydrocracking unit in line 32 are combined and processed in afluid catalytic cracking unit 34. The principal products of the fluidcatalytic cracking unit are gases, including hydrogen, methane andethane, discharged through line 36, C through C gases, dischargedthrough line 38, a fluid catalytic cracked gasoline boiling from C to360 F., discharged through line 40, and a heavy cycle oil boiling aboveabout 360 F., discharged through line 42. The heavy cycle oils in line42 are recycled to line 44 and thence to the catalytic cracking unit;and, when a highly aromatic cycle oil is obtained, this material isrecycled to the hydrocracking unit 24 through line 46 controlled byvalve 48. In hydrocracking unit 24, this highly aromatic cycle oil isconverted to light paratfins, naphtha and gas oils. The naphtha orgasoline fractions from the distillation unit 10, the hydrocracking unit24 and the catalytic cracking unit 34 are combined and sent to a highseverity reforming unit 50. The principal products of the reforming unit50 are hydrogen, methane, and ethane, discharged through line 52, C andC gases, discharged through line 54, and a liquid reformate of highlyaromatic character, discharged through line 56. The reformate is thenpassed to solvent extraction unit 58 where aromatics are selectivelyremoved by an aromatic selective solvent and an essentially non-aromaticraflinate is formed. The non-aromatic raffinate is recycled to the fluidcatalytic cracking unit 34 through line 60 for further conversion toaromatics and principally light paraflins and olefins. The aromaticextract is divided into a high purity benzene, discharged through line62, high purity toluene, discharged through line 64, high purity xylenedischarged through line 66, and a C aromatic fraction. The toluenefraction is passed to the hydrodealkylation unit 68 to producesubstantial quantities of benzene. The benzene from hydrodealkylationunit 68 is discharged through line 70 to a clay-treating unit 72 toproduce a high purify benzene discharged through line 74. This benzeneis combined with the benzene from the reforming unit which has beenseparated in the solvent extraction unit, to produce very substantialyields of benzene per barrel of crude oil fed to the processing system.The xylene fraction is passed to isomerization unit 76 and thence tocrystallization unit 78 through line 80. Substantial amounts ofethylbenzene and paraxy ne are produc d from. the isomerizaton-crystallization operation. From the crystallization unit,ethylbenzene is fractionated out, as an overhead, and recovered throughline 82, and a bottoms fraction of dimethylbenzene is discharged throughline 84. The dimethylbenzene fraction is passed to cooling unit 86 toproduce high purity paraxylene, which is discharged through line 88, anda mother liquor containing orthoand meta-xylene which is recycledthrough line 90 to isomerization unit 76. This recycle is practiced toextinction of the orthoand metaxylene. As an alternative, theisomerization unit can be operated with an isomerization catalystcapable of converting ethylbenzene to dimethylbenzene and the abovecrystallization and isomerization steps can be operated with recycle toextinction. The C aromatic fraction, produced from the extract ofextraction unit 58, can be separated, as by fractionation, to producehigh purity pseudocumene and tetramethylbenzene, which are dischargedthrough lines 92 and 94, respectively. The tetramethylbenzene is passedto crystallization unit 96 to obtain high purity durene, dischargedthrough line 98. The mother liquors of the crystallization unit 96,containing isodurene and prehnitene are discharged through line 100 toisomerization unit 102. In isomerization unit 102, these materials areconverted to further amounts of durene which are recycled tocrystallization unit 96 through line 104. Here again, thecrystallization-isomerization is carried out with recycle to extinction.

The light paraffin-olefin fraction from the catalytic cracking of gasoils and reformate raflinates, is processed in polymerization unit 106.In this unit, the olefins are converted to polyolefinic materialsboiling above gasoline. The polyolefinic material is discharged throughline 108 to hydrogenation unit 110. In hydrogenation unit 110, thepolymers are converted to isoparaflinic materials highly useful as jetfuels and white oils, discharged through line 112, and high octanegasoline, which is discharged through line 114. Light parafiins areseparated and discharged through line 116. The light paraffin fractions(propane, butane, pentane) from distillation unit 10, hydrocracking unit24, reforming unit 34 and hydrogenation unit 110 are passed todehydrogenation unit 118 through line 120. The dehydrogenation unit 118produces a mixture of paraflins and olefins which is discharged throughline 122. This mixture is processed in polymerization and hydrogenationunits 106 and 110 to yield additional quantities of isoparaflins for useas jet fuels and white oils. Unconverted light paraflins are recycled todehydrogenation unit 118 through line 124 for conversion to furtherquantities of olefins. A by-product of the dehydrogenation unit is alarge volume of high purity hydrogen discharged through line 126. Thishydrogen is, of course, useful in the operation of the hydrodealkylationand the hydrocracking units. Further, substantial volumes of olefins areproduced in the dehydrogenation unit which may be separated through line128 and purified for ultimate product use.

While conventional petroleum refining techniques yield 50% or more ofautomotive gasoline per barrel of crude oil processed and treat theheavier liquids for use as home and factory fuels, the present systemyields 70% or greater per barrel of crude oil of pure hydrocarbons ofextremely high value.

Hydrocracking unit 24 may be a conventional hydrocracking meansemploying two-stage hydrocracking containing a conventionalhydrocracking catalyst, such as a precious metal on silica-alumina. Thehydrocracking unit is operated at a pressure above about 500 p.s.i.g.,and preferably 1000 to 3000 p.s.i.g., a temperature of about 400 to 850F., a hydrogen feed rate of about 1000 to 20,000 s.c.f. per barrel,preferably 2000 to 10,000 s.c.f. per barrel, of feed, and at a liquidhourly space velocity of about 0.3 to 5.0.

The hydrocracking unit may be supplied with hydrogen from the reformingand dehydrogenation operations,

Rather than employ a two-stage hydrocracking unit, it is also possibleto employ a hydrofining unit followed by a single stage ofhydrocracking. In this instance, the hydrofining catalyst will be aconventional catalyst such as nickel-molybdate on alumina. Processingconditions for the removal of nitrogen-sulfur compounds from the feed inthe hydrofining unit and to saturate olefins and aromatics include aliquid hourly space velocity of about 1 to 3, a temperature of about 650to 800 F., a pressure of about 500 to 2000 p.s.i.g., and a hydrogen rateof about 1000 to 10,000 s.c.f. per barrel of feed.

Catalytic cracking unit 34 preferably utilizes a conventional fluidcracking catalyst such as fluidized silicaalumina, a pressure of aboutto 50 p.s.i.g., a temperature of about 850 to 1100 F., a catalyst to oilratio of about 2/1 to 5/1, and a reactor space velocity of about 0.5 to5.0.

Catalytic reforming unit 50 utilizes a conventional reforming catalystsuch as platinum on alumina. However, the conditions of operation aresubstantially higher than conventional conditions in order to maximizethe production of aromatics and hydrogen. The high severity reformingconditions employed include a temperature of about 900 to 1000 F., apressure of about 50 to 200 p.s.i.g., a liquid hourly space velocitybetween about 1 ano 10, and a hydrogen rate of about 2000 to 10,000s.c.f. per barrel of feed. A hydrofining section may also be included inadvance of the reforming unit for the removal of nitrogen and sulfurcompounds from the feed. This hydrofining unit will also contain aconventional catalyst, such as nickel-molybdate on alumina, and beoperated under conditions including a temperature of about 600 to 800F., a pressure of about 200 to 1000 p.s.i.g., a liquid hourly spacevelocity between about 1 and 10, and a hydrogen rate of about 200 to2000 s.c.f. per barrel of feed. A conventional hydrogen purificationunit adapted to remove light paraflins from reformer gases to yield ahigh purity hydrogen stream may also be combined in reformer 50.

The solvent extraction unit 58 is preferably a unit employing a solventsystem selective for aromatic materials. Specifically a mixture ofglycols and water may be utilized. The aromatic extract from extractionunit 58 is subjected to conventional fractionation yield pure aromaticfractions. These fractions are sent to their respective processing zonesfor further conversion and/or end product use.

The hydrodealkylation unit 68 may also be conventionally operated,utilizing a catalyst, such as chromia on alumina, at a temperature ofabout 1000 to 1400 F., a pressure of about 400 to 1000 p.s.i.g., aliquid hour- 1y space velocity of about 0.5 to 5.0 and a hydrogen rateof about 1000 to 4000 s.c.f. per barrel of feed. Hydrogen for thehydrodealkylation unit may also be supplied from the reforming anddehydrogenation operations. Benzene from the hydrodealkylation unit ispreferably distilled and hot clay treated at a temperature of about 100to 400 F. and a pressure of about 100 to 1000 p.s.i.g.

The isomerization-crystallization system for treating the xylene streamcan be one of a series of such systems. The crystallization zone maycontain 1 to 3 cooling stages in a temperature range from about 25 C. to50 C. The isomerization zone can be a fixed or moving bed system.Isomerization can be utilized in the treatment of an ethylbenzene-richor an ethylbenzene depleted stream. Isomerization, in this instance, canbe practiced in the presence of a conventional catalyst such as platinumon silica-alumina and under conditions including a temperature of about800 to 950 F., a pressure of 50 to 200 p.s.i.g., a liquid hourly spacevelocity of 0.5 to 10, and a hydrogen rate of about 500 to 3000 s.c.f.per barrel of feed.

Ethylbenzene can be removed from ethylbenzene-rich xylene streams byconventional fractionation such as superfractionation in a distillationcolumn having about 200 to 300 theoretical trays. Theethylbenzene-depleted xylene stream can be isomerized under conventionalconditions in a fixed or moving bed of an isomerization catalyst, suchas silica-alumina. Temperatures of about 600 to 900 F., a pressure ofabout 0 to 1000 p.s.i.g., a liquid hourly space velocity of about 0.5 to10, and a hydrogen rate of about 0 to 1000 s.c.f. per barrel of feed canbe utilized.

Polymerization unit 106 is operated under conditions such that gasolineproduction is suppressed. More specifically, the polymerization zoneutilizes a catalyst, such as boria-alumina, at a temperature of about 75to 400 F.; a pressure of about to 1000 p.s.i.g.; a liquid hourly spacevelocity of about 0.2 to 5.

Hydrogenation unit 110 employs a catalyst such as platinum on alumina,at a temperature of about 200 to 600 F., a pressure of about 100 to 1000p.s.i.g., a liquid hourly space velocity of about 0.5 to 5.0, and ahydrogen rate of about 500 to 3000 s.c.f. per barrel of feed.

The dehydrogenation unit 118 may utilize a catalyst, such as chromia onalumina at a temperature of about 900 to 1200 F., a pressure fromatmospheric to subatmospheric, a liquid hourly space velocity of about0.5 to 10, and a gas dilution ratio of about 0 to 20 moles of gas permole of feed.

To the extent olefins are to be withdrawn for chemical use, conventionalseparation means, such as distillation, or selective solvent extraction,may be employed. Olefin separation can also be effected by passing thedehydrogenation unit product through the polymerization zone withrecycle of the unconverted light paraffins to essential extinction.

Having described the present invention in detail with reference to aspecific flow diagram and specific examples, it is to be understood thatthese are by way of illustration only and that the present invention isto be limited only by the appended claims.

I claim:

1. A method of producing substantial volumes of ammatic hydrocarbons,comprising:

(a) subjecting a broad boiling range hydrocarbon oil to distillation toseparate the same into: (1) gaseous C C and C fractions, (2) a liquidfraction having a boiling range between about C and 360 F., (3) a lightgas oil boiling between about 360 and 600 F., and (4) a residuumfraction boiling above 600 F.;

(b) subjecting said fraction boiling above 600 F. to hydrocracking inthe presence of a hydrocracking catalyst at a pressure of about 500 to3000 p.s.i.g., a temperature of about 400 to 850 F., a liquid hourlyspace velocity of about 0.3 to 5.0 and at a hydrogen rate of about 1000to 20,000 s.c.f./bbl. to produce:

(1) a gaseous C C and C fraction,

(2) a naphtha fraction boiling between about C and 360 F., and

(3) a light gas oil fraction boiling above about (c) subjecting saidfraction boiling between 360 and 600 F. (a) from said distillation andsaid fraction boiling above 360 F. from said hydrocracking of (b) tofluid catalytic cracking in the presence of a cracking catalyst at apressure of about 0 to 50 p.s.i.g., a temperature of about 850 to 1100F., a catalystto-oil ratio between about 2:1 and 5:1 and a reactor spacevelocity of about 0.5 to 5.0 to produce:

(1) a gaseous C C and C mixture of parafiins and olefins,

(2) a gasoline fraction boiling between about C and 360 F., and

(3) a heavy cycle oil fraction boiling above about (d) recycling saidfraction boiling above 360 F. from said catalytic cracking of (c) tosaid catalytic cracking in (c);

(e) subjecting said C C and C fraction from (c) to polymerization in thepresence of a polymerization catalyst at a pressure of about 100 to 1000p.s.i.g., a temperature of about 75 to 400 F. and a liquid hourly spacevelocity of about 0.2 to 5.0 to produce gasoline and a polyolefinicproduct boiling above gasoline;

(f) subjecting said polyolefinic product from (c) to hydrogenation inthe presence of a hydrogenation catalyst at a pressure of about 100 to1000 p.s.i.g., a temperature of about 200 to 600 F., a liquid hourlyspace velocity of about 0.5 to 5.0 and a hydrogen rate of about 500 to3000 s.c.f./bbl. to produce a gaseous C C and C fraction, a gasolinefraction and an isoparaffin fraction;

(g) subjecting said C to 360 F. fraction from said distillation in (a),said C to 360 P. fraction from said hydrocracking in (b) and C to 360 F.fraction from said catalytic cracking in (c) to reforming in thepresence of a reforming catalyst at a pressure of about 50 to 200p.s.i.g., a temperature of about 900 to 1000 F., a liquid hourly spacevelocity of about 1 to and a hydrogen rate of about 2000 to 10000s.c.f./bbl. to produce:

(1) a gaseous C and C fraction and (2) a liquid reformate fraction;

(h) subjecting said liquid reformate fraction from (g) to solventextraction to separate the same into a nonaromatic raffinate fraction,benzene, a toluene fraction, a xylene fraction, and an aromatic C plusfraction;

(i) subjecting said toluene fraction from said extraction in (h) tohydrodealkylation in the presence of a hydrodealkylation catalyst at apressure of about 400 to 1000 p.s.i.g. a temperature of about 1000 to1400 F. a liquid hourly space velocity of about 0.5 to 5.0 and ahydrogen rate of about 1000 to 4000 s.c.f./ bbl. to produce benzene;

(j) subjecting said xylene fraction from (h) to hydroisomerization inthe presence of an isomerization catalyst at a pressure of about 50 to200 p.s.i.g. a temperature of about 800 to 950 F. a liquid hourly spacevelocity of about 0.5 to 10 and a hydrogen rate of about 500 to 3000s.c.f./bbl. to produce ethylbenzene and dimethylbenzenes;

(k) separating paraxylene from said dimethylbenzenes and recycling theremaining portion of the isomerizate from (j) to the isomerization in(j) until essentially all of the orthoand metaxylenes therein areeliminated;

( 1) subjecting the C -PlUS fraction from said extraction in (h) toseparation to produce pseudocumene durene, isodurene, and prehnitene;

(m) subjecting said isodurene and said prehnite ne to isomerization inthe presence of an isomerization catalyst at a pressure of about 0 to1000 p.s.i.g. a

temperature of about 600 to 900 F. a liquid hourly space velocity ofabout 0.5 to 10 and a hydrogen rate of about 0 to 1000 s.c.f./bbl.,

(n) subjecting said non-aromatic raflinate from said extraction to saidcatalytic cracking in (e); and

(o) subjecting said gaseous C C and C fractions of (a)(1), (b)(1, (f)and -(g)(1) to dehydrogenation to produce a mixture of paraffins andolefins.

2. .A method in accordance with claim 1 wherein the heavy cycle oilboiling above 360 F. from the catalytic cracking in (c) is subjected tothe hydrocracking when the aromatic content thereof has increased to apoint where said aromatic content is predominant.

3. A method in accordance with claim 1 wherein the solvent extraction in(h) is carried out by means of a glycol-water solvent.

4. A method in accordance with claim 1 wherein the isomerizationcatalyst utilized in the isomerization of the xylene fraction in (j) isselected to convert the ethylbenzene to xylenes.

5. A method in accordance with claim 1 wherein the C C and C fractionsfrom the distillation, in (a), the hydrocracking, in (b), the reforming,in (g), and the hydrogenation in (e) are subjected to dehydrogenation inthe presence of a dehydrogenation catalyst at a pressure of aboutatmospheric to subatmospheric, at a temperature of about 900 to 1200 F.,a liquid hourly space velocity of about 0.5 to 10 and while maintaininga gas dilution ratio of about 0 to 20 moles of gas per mole of feed andthe product of said dehydrogenation is subjected to the polymerization.

6. A method in accordance with claim 5 wherein C C and C parafiins areseparated from the dehydrogenation product and recycled to thedehydrogenation.

7. A method in accordance with claim 5 wherein a portion of the olefiniccontent of the dehydrogenation product is separated therefrom prior topassage of said dehydrogenation product to the polymerization.

8. A method in accordance with claim 1 wherein the hydrogen oil is apetroleum crude oil.

9. A method in accordance with claim 1 wherein the hydrocarbon oil is anoil obtained from solid carbonaceous materials.

10. A method in accordance with claim 1 wherein the polymerizationcatalyst is boria deposited on an alumina base.

References Cited UNITED STATES PATENTS 3,172,842 3/1965 Paterson 2083,185,639 5/1965 Paterson 208-68 3,409,540 11/1968 Gould et al 208-79DELBERT E. GANTZ, Primary Examiner G. E. SCHMITKONS, Assistant ExaminerUS. Cl. X.R.

